Soil Nitrogen Losses

Fall application of fertilizer can reduce the workload in the spring. Reducing the workload in the spring allows earlier seeding and better yields. The problem with applying fertilizer in the fall is that some of the nitrogen will be lost by the time the plants get to use it in the next growing season. These losses can take place through denitrification or through leaching. With the heavy rains that we have seen this fall, the potential losses for nitrogen loss are high. Applying nitrogen in the spring will give the best nitrogen utilization. Using a band for fertilizer application is better than broadcasting. Soils that are too wet are more likely to see denitrificaiton and leaching happen. Warmer soils are prone to more losses than colder soils. Fertilizer type can impact fertilizer availability. Knowing all these factors will help get the best bang for your nitrogen dollar. Applying fertilizer in the fall has never been my first choice for nitrogen. The potential for losses of this nitrogen is high in our country. If nitrogen is lost, we lose yield potential as well as the actual nitrogen itself. With the soil moisture that we have now, the potential losses could easily run in the 10% range. If a producer applies 60 pounds of nitrogen per acre, the nitrogen losses would be at 6 pounds per acre. This represents about a $3.60 per acre loss if we assume nitrogen is worth about 60 cents per pound. With 6 pounds of nitrogen loss, there is also a yield loss. It takes about 2.1 pounds of nitrogen to produce a bushel of wheat. This represents a potential yield loss of 2.9 bushels per acre. Wheat is now worth about $7 per bushel so this represents a potential dollar loss of $20.30 because of the yield that is lost. You add these two numbers up and there is a reduction of about $24 per acre. This is significant on anyone’s bottom line. There are ways to reduce the potential losses of nitrogen in the fall. Applying any form of nitrogen later in the fall will help reduce losses. Once the soil has cooled off, the bacteria in the soil have slowed down and the potential for loss is reduced. Using additives with your nitrogen will help reduce losses. There are products that can be added to anhydrous ammonia as well as urea that can help reduce the losses of nitrogen that is applied in the fall. Banding of nitrogen will reduce the exposure of the nitrogen to the soil microbes and reduce the potential losses. These management practices help, but they do not always eliminate the potential nitrogen losses. If we are to grow more bushels, we need to have the nutrients available to do it. The environment in our soils can be harsh on the nitrogen that we apply. Spring application of nitrogen is the best way to go. If our seeding equipment has the capability, applying the nitrogen you require will give the best bang for your fertilizer dollar.


By Dave Cubbon, P Ag